1. Related Applications
U.S. Patent Application Ser. No. 740,707 filed Nov. 11, 1976, now U.S. Pat. No. 4,068,994, entitled "Apparatus for the Printing of Ceramic Green Sheets" by R. H. Cadwallader, Y. Darves-Boronoz, A. S. Gasparri and F. Racine and assigned to International Business Machines Corporation.
U.S. Patent Application Ser. No. 859,777 filed concurrently with the present application entitled "Method and Apparatus for Locating and Aligning Flimsy Sheets" by D. E. Lonser, W. G. Rance, A. A. Stricker and W. VonKaenel and assigned to the International Business Machines Corporation.
2. Field of the Invention
The present invention relates to a vacuum pick up and transfer head for handling flimsy sheets. More particularly, the invention concerns an improved vacuum pick up and transfer head adapted for handling of thin flexible materials such as uncured ceramic green sheet. Such sheets require adequate support at a variety of locations during various stages of process manufacturing, without contact with contaminating objects such as human hands, etc.
In the manufacture of semiconductor devices, multilayer ceramic modules are becoming more widely used. Such modules are comprised of multiple layers of ceramic materials stacked in a particular orientation, with each sheet or layer of ceramic having imprinted thereon a particular conductive pattern. With the entire stack of uncured ceramics in place the stack is pressed and cured to form an integral ceramic package having a large plurality of electrically connected conductive paths arranged therein.
Heretofore, in the manufacture of such multi-layer ceramic packages it has been the practice to handle and stack by hand sheets of uncured ceramic sheet material known as green sheet. Such green sheet is thin, flimsy material which is easily subject to stretching and other deformation, as well as tearing and degradation by contact with human hands, particularly if finger prints are left within a region to be imprinted with conductive material.
Other problems are encountered in obtaining satisfactory alignment of such green sheet and the spacer sheets which are commonly utilized in stacking the sheets within trays to prevent adhesion of sheets to each other. These problems are discussed in more detail in the aforementioned related application by D. E. Lonser et al., describing a Method and Apparatus for Locating and Aligning Flimsy Sheets. However, it should be apparent that a need exists in the art for an effective pick up transfer head for picking up flimsy sheets and transporting them between various process steps without damaging the green sheet. Moreover, a need exists for a pick up and transfer head which is capable of supporting the green sheet both on the periphery and in the center during such handling to prevent stretching and tearing of the green sheet prior to imprinting and/or placement in a final stack. It is also desirable to provide a pick up and transfer head which has a capability of detecting whether a green sheet or a spacer sheet has been picked up, and which includes means capable of positively stripping green sheets and spacer sheets from the head at a predetermined time.